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EWB-USA Technical Paper 104: Fecal Coliform Contamination of Drinking Water ~An Evaluation of Field Assessment Techniques

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Fecal Coliform Contamination of Drinking Water ~

An Evaluation of World Field Assessment Techniques

William Fripp1, Catherine Dane Woodyard, PhD2, and Marina Hanna3

Subject Key Word: Water Supply Key Words: Water supply, water quality, water survey, water treatment, fecal coliform, field test

Abstract: A safe, consistent, and reliable water supply is a universal need. However, a large number of the world’s population lives in areas that are suffering from water quality problems and water shortages. Many areas have contaminated water with fecal coliform bacteria as the primary contaminant of concern. As a result, there are many aid groups that are actively working to develop and improve the water supply in the developing world. An important first step in such work is an accurate appraisal of the existing water supply. This appraisal often requires a rapid, onsite field assessment of possible fecal coliform contamination with minimal equipment. This paper summarizes a qualitative evaluation of five field assessment techniques undertaken by an interdisciplinary team of students involved in aid work. The focus of this evaluation is on Presence/Absence testing. The evaluation examines usability, accuracy, cost, speed of results, and ease of explaining results to the local population. Advantages and disadvantages of each technique have been identified and discussed. The purpose of this paper is to provide guidance that will aid in the selection of a suitable rapid fecal coliform field test.

The team performed their assessments of the five techniques in the United States under controlled situations, as well as during an evaluation trip to Belize. All of the evaluations were conducted under the oversight of a professional engineer with experience in water quality assessments and water treatment design. This study and paper is of value to aid groups involved in the assessment of water projects in the developing world.

Introduction

Water is a basic requirement for human life. Most people in the developed world are fortunate to enjoy a safe, consistent, and reliable water supply. However, there are many areas in the developing world where this is not the case, and water is unsafe for human consumption. 1 Stephen F. Austin State University School of Nursing, Class of 2013 2 University of Mississippi Health Promotion and Behavior, Class of 2013, Tallahatchie General Hospital 3 Texas A&M University Engineering, Class of 2015


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‘Unsafe water’ is water that is contaminated and poses risks to human health. In many cases, the primary contaminant of concern is fecal coliform bacteria. This is bacteria that is found in the large intestine and indicates fecal contamination of the water supply. Those who drink this contaminated water are at much greater risk for waterborne diseases, which globally kills and sickens thousands of people every day. The most prominent example is waterborne diarrheal diseases, which account for 1.8 million child deaths annually (Watkins, 2006). Overall, 3.4 million people die annually as a result of water related diseases, making it the leading cause of disease and death around the world (Prüss-Üstün, 2008). Note that not only do areas with contaminated water have a high incidence of disease, but have also been found to result in statistically shorter children, higher death rates, lower average lifespans, poorer quality of life, increased child mortality rate, and weaker economies.

Areas suffering from poor water sources are more likely to have a socioeconomically depressed populace than those with clean water. Contributing to this poverty, poor water sources often lead to outbreaks of water borne illness, which put an additional strain on these communities, resulting in a direct negative socioeconomic impact. Those who are infected by a waterborne disease are burdened with related costs, such as expenses for medical treatment and loss of manpower. In addition, a family who cannot depend on their water source must travel for their water; as a result, farmers and wage earners are less productive. In developing nations, women walk miles every day for water, wasting hours that could have been used more efficiently elsewhere.

For these reasons, halving the number of people without sustainable access to safe drinking water was placed among the eight Millennium Development Goals (WHO, 2013), which were established following the Millennium Summit of the United Nations in 2000. Testing for and identifying poor water quality sources are vital steps in continuing the purpose of this goal. Both secular and religious aid groups have long focused on water development projects as well.

In the developed world, there are a variety of established practices and procedures which, if followed, assure a consistently safe water supply. However, the use of these techniques and practices requires equipment and testing that is often not available for short term projects in the developing world. Many aid groups must rely on experience, interviews, and rapid field tests to ascertain water quality. This paper reviews the use of five rapid field tests.

The techniques and procedures presented in this paper are applicable where conventional water testing approaches are not possible. The focus of these techniques is on achieving ‘good enough’ results which can be appropriate for many limited resource conditions that are characteristic of the developing world. However, the field tests presented are not always appropriate. Health practitioners and engineers must make the decision as to when they are appropriate. It is incumbent upon the members of the team to use their skills and understanding of the situation to assure that the ad-hoc approaches are the best that can be achieved for the project being constructed.


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Why Test in the Field?

Water quality development aid work often begins in an area where the population is suffering from recognizable symptoms of waterborne diseases or where new access to water is to be established. In order to address either of these issues, there first needs to be an accurate assessment of the water quality.

In the developing world, many communities have water distribution systems in place. Some of these distribution systems were never effective in delivering safe, clean water, while others were effective at one time, and still others are effective only during certain seasons. Past performance, however, is by no means an accurate measure of the current water quality. Many water systems with unsafe drinking water once had systems that functioned correctly, but have declined due to lack of maintenance. Tests need to be conducted on the water that the community currently uses to quantify the potential issues.

Many communities in the developing world are unaware of the hazards that unsafe drinking water may pose and do not understand what may be causing their ever-present illnesses. Residents may assume that disease may be related to food, bathing water, drinking water, air, or caused by the supernatural. Testing allows aid workers to better quantify the potential problem. Testing and interpreting the results in the field allows local community members and participants to see the information which facilitates better acceptance of the results and ultimately leads to a proposed solution or treatment. Many members of impoverished and disadvantaged communities are distrustful of authority. A field test that they understand is empowering to the community and helps them become part of the decision making process.

It is often illegal to carry water samples across international borders without obtaining special permission. If a laboratory is to be used as part of a test, it must be done in the country where the sample is obtained. However, even this can be problematic due to transportation issues that can be prevalent in the developing world. Taking water samples and shipping them back to a lab exposes the samples to potential alteration. Simply leaving samples in the sun or allowing too much time in shipment can sterilize bacterial samples, yielding inaccurate results. Inaccurate results provide misinformation, placing those at risk who might otherwise have received warning that their water source was unsafe. For this reason, it is important to conduct testing onsite and in the field.

Indicator Organisms

Directly testing for harmful pathogens among fecal coliforms in a water supply is impractical, as it requires lengthy, complex, and expensive testing procedures. For this reason, testing for indicator organisms is the norm. The World Health Organization (WHO) recommends the use of indicator testing for water quality (WHO, 2008). Indicator organisms are bacteria that have been found to be present when certain pathogens are present, and absent when those pathogens are absent. These indicator organisms are usually not pathogenic themselves, but are of similar fecal origin.


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The presence of fecal coliform bacteria in drinking water is strong evidence of fecal (sewage) contamination. This is a significant health problem, as fecal coliforms frequently co-exist with human pathogens. While other vectors of disease exist, water is a necessity to all people and contaminated water can easily sicken a community without intervention.

There are a range of tests that are available and suitable for use in low resource areas by aid groups. Many test for E. Coli or total coliform. These are widely accepted but it must be noted that there are naturally occurring coliforms in the environment that are not harmful and not an indicator of fecal contamination. This is particularly an issue in tropical areas and can result in tests indicating contamination where none is present. An alternative to this is an assay that tests for hydrogen sulfide (H2S) production. Several indicator organisms for fecal coliforms produce hydrogen sulfide as a product of their metabolism. In these tests, a medium is added to a water sample, which turns black and takes on the ‘rotten egg’ odor if the hydrogen sulfide producing organisms are present. This result indicates that other fecal pathogens are present in the water, posing a significant health risk. However, the use of H2S tests are not universally accepted at this time (Sobsey and Pfaender, 2002; Wright et. al. 2012).

Presence/Absence Testing

As indicated in the name, Presence/Absence Testing is a broad category of tests which indicate if a particular contaminant is present or absent. Presence/Absence tests are assays that provide simple interpretation of results. Should a water sample have a concentration of indicator organisms above zero, the result will show positive; whereas if the water sample was completely free of indicator organisms, the result would show negative. Such testing does not tell the user the amount of contaminations but simply that there is contamination. Therefore Presence/Absence Testing is not generally appropriate as the sole testing for substances where a small amount of contamination is acceptable. However, they are appropriate in some conditions and especially in field expedient conditions for dangerous pathogens.

As the EPA considers the concentration of fecal coliforms in a water supply above zero to be of ‘urgent public concern,’ assays that test for these indicator organisms are normally used in a Presence/Absence fashion. Should a single water quality sample return positive, it is considered to be “strong evidence of recent sewage contamination.” (EPA 1990). EPA requirements state “Public water systems need only determine the presence or absence of fecal coliforms; a determination of fecal coliform density is not required.” (EPA, 2009). While the current study focuses on the use of field tests for Presence/Absence assessment, it should be noted that some organizations use count for decision making tools and a coliform count of more than zero may be acceptable in some situations.


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Most Probable Number

A Most Probable Number (MPN) test uses a series of incrementally diluted Presence/Absence tests to estimate a number of bacteria in a given sample. This procedure provides an estimate rather than an exact number of bacteria in a sample. A MPN can be useful in comparing water quality of different sources. It can also be used to evaluate water that is used for bathing, swimming, or drinking in some circumstances.

Water Quality Tests Evaluated

The subject analysis selected five readily available indicator tests for comparison. These have all been used in various capacities by advisors to the authors to assess and monitor water quality on a variety of projects. The five tests selected are listed below:

1. HACH PathoScreen o The PathoScreen by HACH is a Presence/Absence test designed for field

testing of water to detect indicator organisms of fecal origin. The indicator is H2S. Samples are taken in 20 mL glass vials and provided a growth medium. Results are determined by observing for a color change. This test can be used to estimate a Most Probable Number.

2. 4-Methyl Umbelliferyl Beta Glucuronidase (MUG) o The ‘Mug’ Test is a Presence/Absence test designed to test for Coliform

bacteria in sample water. It is built as a ‘mug’ or jar that is filled with 120 ml of sample water and the included growth medium. Results are determined by observing for a visual color change of the medium, and the use of UV light to test for E. Coli. Results indicate presence or absence of Coliform bacteria.

3. 3M Petrifilm Coliform Count Plate o 3M Petrifilm Coliform Count Plate is a film plate containing an agar. A

sample is placed on this plate and the results are read by enumeration of visible growth colonies along with associated gas bubbles. A colony count number which can be interpreted as a Presence of contamination is the product of this test.

4. Watersafe Test Strips o The WaterSafe Test is a Presence/Absence test that tests for coliform

bacteria. The test is often used to test swimming pool water. Small water samples are taken in plastic vials with a strip placed inside. Results are determined by counting the number of lines on the strip. It is strictly a binary test as it indicates ‘safe’ or ‘contaminated’.

5. LaMotte Coliform o The LaMotte Coliform test is a Presence/Absence assay that tests for

coliform bacteria in sample water. Results are read by a visual color change of the sample medium. The LaMotte Coliform can also be used to estimate a Most Probable Number.


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Evaluation Approach

The evaluation was done in two phases in two locations. The first phase was with controlled samples in the United States. Water that was known to be contaminated and known to be uncontaminated was tested by individuals who had been trained in a one day water quality workshop. The individuals trained had participated or were interested in participating in religious based mission trips to the developing world. All were educated but none had specific training in water quality evaluation. They were provided lectures describing each of the techniques and were then asked to demonstrate and perform the evaluation techniques on the water samples.

The second phase of the evaluation was accomplished during a field assessment reconnaissance as part of an Engineers Without Borders (EWB-USA) trip to a impoverished community (locally referred to as a ‘slum area’) in Belize. During this EWB reconnaissance aid trip, various water quality testing methods were conducted in the field. The testing was done to determine the quality of the water used by the residents of the community, following reports of poor plumbing practices and the presence of standing, untreated sewage. Testing was accomplished by both undergraduate and graduate college students representing various disciplines and under the guidance of a professional engineer with experience in domestic and foreign assignments involving water quality testing.

During and after these evaluations, notes were taken and compiled about the different test procedures. The attributes of each were considered based on the evaluation basis described in the next section. Photos of these evaluations are provided in Figure 1.

Figure 1: Use of field tests. Left to right- Workshop in the United States, Instruction in the field, Field Application of testing in Belize

Evaluation Basis

The field tests were evaluated based on a variety of parameters that address objectives important to field teams. It is recognized that much of this evaluation is qualitative and that each basis is not directly comparable. Therefore the metrics for each are described below and are generally given scales that are rated relative to one another. In this manner, a user who is considering one or more of the tests under review can make a selection based on information most important to their application.


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Compactness of Equipment/Materials: Most water quality assessment teams in the developing world have to carry equipment and testing materials in backpacks. Onsite water analysis tests need to be small and portable in order to be carried into the field. All of the tests evaluated did not require special heating or cooling nor electrically powered equipment. This objective was evaluated on how easy it was for a team member to carry multiple tests both before and after sampling. The evaluation also considered how easy it was to keep samples from being corrupted after they were obtained since teams often need to conduct multiple tests.

All of the tests could be carried in a backpack and certainly are more compact than conventional laboratory equipment. Therefore this rating is reported as excellent (E), good (G), or fair (F). This rating is assigned based upon how the users and the authors considered that each test satisfied this criterion.

Speed of Obtaining Samples: Many assessment teams have limited time in the field. Also, many of the testing locations may have some inherent physical safety concerns. It is important for tests to be able to be conducted quickly. This comparison was simply made by asking users how long it took them to take and prepare samples using the different tests. For this criterion, each test was rated as excellent (E), good (G), or fair (F). This rating is assigned based upon how the users and the authors believed each test compared to the others in satisfying this criterion.

Speed of Results: The speed of results is critical in selecting a water quality test. If a water quality testing team is testing an area requiring international transportation, the turnaround times on the tests will need to be considered. They will determine the true window of availability for sampling during the time that the testers are on site. Many tests require up to three days for a reliable result. Since carrying water samples across national borders may be prohibited, results may not be usable if the appropriate window of time has not elapsed by the time the team needs to travel home. For this criterion, each test was rated as excellent (E), good (G), or fair (F). This rating is assigned based upon how each test compared to the others in satisfying this criterion.

Easy to Learn: All team members should be able to accurately and consistently collect samples and conduct the tests. Testers who are unfamiliar with the testing/sampling process waste valuable time during the tester’s window of availability. It is also recommended that local decision makers be involved in testing as much as possible to facilitate local ‘buy in’ of the results and ultimate recommendations. Therefore the ease of learning the tests and their ease of repeated use is critical toward test selection. Each test was rated as excellent (E), good (G), or fair (F). This feature was evaluated by ease of explaining the testing procedures to the participants in the EWB trip and during the workshop held in the United States.

Accuracy of Results: Accurate information is critical for any decision making process. False positives and false negatives can be very detrimental to an evaluation effort and ultimately to the health of the community. The evaluation did not include a microbiological assessment. It is assumed that what is reported by the manufacturer is


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accurate. Rather this evaluation assessed accuracy by how well the tests indicated the same result for samples of unknown quality and how well they indicated results of samples of known quality. In this manner all potential sources of inaccuracy (test quality, test fragility, user issues, etc) are grouped together. Each test was rated as excellent (E), good (G), or fair (F). A rating of ‘Excellent’ indicates that the test had near 100% accuracy. A rating of ‘Good’ was assigned to a test with 75% accuracy. Lastly, a rating of ‘Fair’ was assigned to any test with less than 75% accuracy. Again, it should be noted that such evaluation includes operator error in field applications, ability to store, transport, and measure samples.

Ease of Explaining the Results: For any work to be effectively accomplished in a community, the results need to be accepted by members of that community. The results of the testing have to be readily apparent to people who may only have a rudimentary understanding of water quality issues. This was assessed qualitatively in public meetings and to individuals in Belize, as well as during the workshop in the United States. For this criterion, each test was rated as excellent (E), good (G), or fair (F). This rating was assigned based upon how the users and the authors felt each test compared to the others in satisfying this criterion.

Cost of Test: Many efforts in the developing world operate on a limited budget. A low cost per test generally assures that the team will conduct multiple tests and obtain sufficient practice before they deploy to a site. This comparison is a simple relative cost per test and associated required equipment at the time of this evaluation.

Results of Evaluation

The results of this evaluation are provided in Table 1. An asterisk (*) is placed in the matrix box to indicate which test the authors believed best satisfied criterion listed in the column. As noted earlier, it is recognized that much of this evaluation is qualitative. Further explanation of the evaluation for each test is provided after the table.

Table 1: Evaluation of Field Assessment Techniques Test Compact Sample

Speed Result Speed

Easy to Learn

Accuracy Ease to Explain

Cost1

PathoScreen E G G E E* E* $0.80 Mug F E* G E* E G $12.003M Petrifilm F G G G G F $1.50 Water safe test strip

E* F E* E F F $2.75

Lamotte E G G F E G $3.00 1- Costs at time of evaluation, 2012/2013

HACH PathoScreen: The Hach PathoScreen test kit was easy to use in the field and requires only a small space in one backpack. It tests for H2S, produced by H2S producing Coliform bacteria. Since there are many types of E. Coli that are indigenous to certain waters and are not of fecal origin, this test helps to reduce false positives in


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tropical situations. This test uses a growth medium carried in small, individual pillow packs which are placed in tubes for incubation. Users can readily supplement the five tubes that are provided in the Hach kit with additional sample tubes so that multiple and repeat samples can be obtained. Since the growth medium is provided in sealed pillow packs, the vials can be reused after careful cleaning and disinfection. Users need to obtain pipettes to obtain sampling from the point of interest.

This test produced results that were easy to explain. As the test is a Presence/Absence test, a negative or ‘clean’ result is straw yellow, and a positive or ‘contaminated’ result is black. Results are visible in one to two days. Several residents of the community where the tests were conducted were shown a positive result and were heard saying ‘It looks like death,’ indicating appropriate understanding of the test result. An example photograph is provided in Figure 2.

Figure 2: Results of a positive (black) and negative (straw yellow) of the Hach PathoScreen test.

In addition to successfully producing results congruent with known water quality samples, multiple samples were drawn on the same sites in the field, which consistently produced identical results. This is an excellent test kit for where multiple samples are needed and when clear public explanation is critical.

Mug Test: The Mug test kit is a large container which contains the growth medium. It is simple to use; one merely fills the container with sample water. Results are obtained in two to three days. A change in color to blue-green indicates the presence of coliforms. The sample fluoresces under a UV light if E. Coli is present (Figure 3). Users found that the size of the mug is cumbersome and limits how many tests a team can collect and store. In addition, these tests are relatively expensive. Nevertheless, this is a good solution if only a few samples need to be evaluated.


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Figure 3: Mug Test results. Left to right - initial sample, positive result and two days after sample, and fluorescence under UV light indicating positive result

3M Petrifilm Coliform Count Plate: This test is cheap, requires minimal equipment, and needs very little space for storage of the tests before use. Multiple tests are provided in a sealed packet that is fairly robust. However, once opened, significantly more care is required and the growth medium must be protected from excessive heat and humidity. Incubation must is recommended to be above 35 degrees C (95 F). When testing in the tropics, achieving this temperature is not a concern. In colder areas, the participants in this study used chemical hand warmers, as well as sealing them in plastic bags and ‘wearing’ them in their clothing to accomplish incubation in the field.

As the test requires a level, flat surface to work on (and a non-windy environment), this test proved difficult to perform. Another significant drawback to this water quality test is the small sample size and sensitivity. The petrifilm is designed for tests of concentration with a sensitivity minimum of 100 colony forming units per 100mL. Since water is considered contaminated regardless of concentration above zero, the purpose of this test becomes Presence/Absence of coliform bacteria. Unfortunately, this assay is only capable of testing 1 mL of water, which is very small in volume and therefore provides little certainty of a negative result. Some tests of known poor water did not produce an expected result indicating contamination.

Results are apparent in two days. However, results can be difficult to explain. While the laboratory look of it is initially attractive to young people from the developed world, it appears to be just “so many little dots” on a sheet for comparatively unsophisticated residents of a disadvantaged community. These dots are not obviously ‘bad’. An example is provided in Figure 4.


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Figure 4: 3M Petrifilm

Finally, if multiple tests are obtained and transported, special precautions are needed to prevent corruption of the results. They can be readily over heated in a backpack as the manufacturer notes that temperatures above 25 degrees C (77 F) can damage opened test pouches. In addition, samples can bleed across the surface and out of the sheet and users in this study were concerned about cross contamination between sample plates.

Watersafe Test Strips: This Presence/Absence test was relatively cheap, easy to perform, and provided quick results. Multiple tests can be readily carried and each is contained in a sealed foil pack. The results are available in 20 minutes but require that the user does not disturb the sample during that time. As a result, the user must stay at the site and ‘watch’ the sample vial. A positive result is indicated by lines on a test strip (Figure 5). It is a good test for rapid evaluations of total coliforms.

Figure 5: Watersafe test and results. A positive result is indicated by two lines

However, there was significant question as to the accuracy of the results. Several tests returned results contrary to the known water quality. In addition, this test uses very


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small sample sizes and is not approved for the testing of drinking water. The sample indications are not always apparent to the locals and the indicated lines can rapidly fade. Finally, the provided syringes are small and encourage ‘top sampling,’ which is an incorrect sampling practice.

LaMotte Coliform: This test is relatively easy to carry. The tests are provided in vials that have the growth medium already added by the manufacturer. As a result, the user cannot reuse the vials. Sample water is mixed in a whirl bag and placed in the vials. Results are indicated by a color change which is apparent in two days. A negative test is red and a positive test is yellow with gas bubbles (Figure 6).

Figure 6: Lamotte results. Positive result is yellow

The major drawback of this test is that the results are not intuitive. While they are obvious and readily interpreted, the color change is not obviously ‘bad’.

Conclusion

The evaluation of potential fecal contamination of water supplies provides vital information for work on potable water systems in the developing world. Such important testing can be challenging in field situations where testing staff has limited training and when resources are limited. The five tests evaluated in this study are all good tests and are all applicable for certain situations. Overall, the users involved in this study preferred the Hach PathoScreen test over the other aforementioned techniques. However, it is incumbent upon the leader of any aid trip to evaluate and select techniques based on site specific conditions.

References

EPA (2009). Analytical Methods Approved for Drinking Water Compliance Monitoring under the Total Coliform Rule, 40 CFR 141.21.

EPA (1990). Environmental Pollution Control Alternatives: Drinking Water Treatment for Small Communities.. EPA/625/5-90/025 (NTIS PB91145961)


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Sobsey, M.D. and Pfaender, F.K. (2002) Evaluation of the H2S Method for Detection of Fecal Contamination of Drinking Water. World Health Organization, Geneva Switzerland

Watkins, K. Human development report 2006. beyond scarcity: Power, poverty and global water crisis.. Retrieved from http://hdr.undp.org/en/media/HDR06-complete.pdf

Wright, J.A.; Yang, H.; Walker, K.; Pedley, S.; Elliot, J.; and Gundry, S.W.. (2012), The H2S Test versus Standard Indicator Bacteria Tests for Faecal Contamination of Water: Systematic Review and Meta-analysis. Trop. Med. Int Health 17, 94-105

WHO, (2008), Guidelines for Drinking-Water Quality, Vol 1, 3rd ed. World Health Organization, Geneva Switzerland

WHO (2013). WHO | MDG 7: ensure environmental sustainability. Retrieved September 9, 2013, from http://www.who.int/topics/millennium_development_goals/mdg7/en/index.html